Hydraulics & Stormwater Workbench

Interactive workspace initializes in your browser. Engineering method, assumptions, validation, and references are available below.

Engineering reference

Hydraulics & Stormwater: theory, method, and sources

This civil & structural engineering workspace publishes 11 governing equations, 6 stated assumptions, 1 documented boundary, and 2 sources so the numbers it returns can be checked rather than taken on trust.

Calculations run locallyCalculation & source methodology

How this tool works

Ten modules span pressurized pipe hydraulics, open channel flow, flow measurement devices, and stormwater peak-flow estimation.

Friction losses can be computed with either the Darcy–Weisbach equation using the Swamee–Jain friction factor or the Hazen–Williams equation, so the two common practice methods can be compared on the same system.

Calculators and topics covered

hydraulics
stormwater
pipes
open channels
pumps
Bernoulli
Darcy-Weisbach
Manning equation
Hazen-Williams
orifice
weir
Rational Method

Core equations

\text{continuity:}\quad Q = AV

\text{Bernoulli head:}\quad H = \frac{p}{\rho g} \frac{+ V^{2}}{2 g} + z

\text{Reynolds number:}\quad \mathrm{Re} = \frac{\rho VD}{\mu }

\text{Swamee–Jain friction factor:}\quad f = \frac{0.25}{\left[log_{10} \left(\frac{\varepsilon }{3.7 D} \frac{+ 5.74}{\mathrm{Re}^{0.9}}\right)\right]^{2}}

\text{Darcy–Weisbach:}\quad h_{f} = \frac{f \left(\frac{L}{D}\right) V^{2}}{2 g}

\text{Hazen–Williams:}\quad h_{f} = \frac{10.67\; L\; Q^{1.852}}{C^{1.852}\; D^{4.87}}

\text{Manning open channel:}\quad V = \left(\frac{1}{n}\right) R^{\frac{2}{3}} S^{\frac{1}{2}}

\text{pump power:}\quad P = \frac{\rho gQH}{\eta }

\text{orifice:}\quad Q = C_{d}\; A \sqrt{2 gh}

\text{rectangular weir:}\quad Q = \left(\frac{2}{3}\right) C_{d}\; b \sqrt{2 g}\; H^{\frac{3}{2}}

\text{rational method:}\quad Q = 0.00278 \cdot C \cdot i \cdot A\; \left(\frac{Q\; in\; m^{3}}{s},\; \frac{i\; in\; \mathrm{mm}}{\mathrm{hr}},\; A\; in\; \text{hectares}\right)

Method and assumptions

Assumptions

Flow is steady and incompressible, and water properties are taken at about 20 °C.
Hazen–Williams is valid only for water in the turbulent range; the C value carries all roughness and age effects.
Manning calculations assume uniform flow at normal depth in a prismatic channel.
Orifice and weir discharge coefficients are user-supplied and must match the device geometry and approach conditions.
The rational method assumes a rainfall duration at least equal to the time of concentration and a uniform runoff coefficient over the catchment.
Minor losses are entered explicitly; nothing is added automatically for fittings.

Limitations and design boundaries

Educational screening calculations only. Real systems require survey data, calibrated coefficients, local rainfall criteria, transient and network analysis, environmental review, and applicable design standards.

Sources and references

Primary sources are preferred for ratings, standards, manufacturer data, and externally defined constants.

Source policy

Chow, Open-Channel Hydraulics
Munson et al., Fundamentals of Fluid Mechanics